1. Department of Earth Sciences, ETH Zurich, Zurich, Switzerland.
2. Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland.
3. Department of Geosciences, University of Arizona, Tucson, Arizona, USA.
4. School of Earth and Environment, University of Leeds, Leeds, UK.
5. Géosciences-Environnement Toulouse, CNRS-Observatoire Midi-Pyrénées, Toulouse, France.
6. Swiss Federal Institute for Forest, Snow and Landscape Research, Birmensdorf, Switzerland.